Display screen or portion thereof of a device with transitional graphical user interface



FIG. 1 is a front view of a first image of a display screen or portionthereof of a device with transitional graphical user interface;

FIG. 2 is a front view of a second image thereof; and,

FIG. 3 is a front view of a third image thereof.

The broken line showing of the display screen or portion thereof in allviews forms no part of the claimed design.

The appearance of the transitional image sequentially transitionsbetween the images shown in FIGS. 1-3. The process or period in whichone image transitions to another image forms no part of the claimeddeign.

CLAIM The ornamental design for a display screen or portion thereof of adevice with transitional graphical user interface, as shown anddescribed.